It is known that machines for preparing espresso coffee typically used in bars and restaurants require a dose of roasted and ground coffee to be placed in a filtering vessel which is installed in the machine. This vessel is part of the so-called filter basket holder, which is filled manually with the dose of ground coffee (7±1 g for each cup to be dispensed) and then mounted on the machine in order to proceed with the extraction of the beverage.
Espresso coffee preparing machines are provided internally with a boiler for heating the water taken from a reservoir or other source and with a pump for sending hot water at a selected pressure to the output duct.
The traditional method for extracting the beverage by means of known machines typically consists of a first preinfusion step, in which the flow-rate of water entering at 90±2° C. is reduced for a certain time interval; a second imbibition step; and a third extraction step, in which the pod of coffee is crossed by a flow of hot water at 90±2° C. at a constant pressure of 9 bars when it enters the powdered coffee pod.
The beverage obtained from traditional espresso coffee machines is usually clearly distinguishable from the beverage that can be obtained at the household level with coffee pots or infusion devices, not only because the flavor, aroma and body properties are different, but also because the beverage obtained from traditional espresso coffee machines is characterized by a surface layer of foam, also known as crema. Crema is an attribute of the coffee beverage which is particularly appreciated by the consumer and is also an indicator of the correct preparation of the beverage. The factors that influence the result of crema in the cup are mainly the degree of grinding, the degree of roasting, the carbon dioxide content in the coffee, the temperature and characteristics of the water, the pressure of the water, the temperature of the assembly, the temperature of the cup, the time elapsed between preparation and consumption, the method for conveying the beverage from the extraction chamber to the cup, the level of cleanliness and the efficiency of the extraction assembly.
As stated in international applications WO 2005/092160 and WO 2005/092162, as well as in European patent application 05020525.1, the Applicant of the present patent application has designed a particular cartridge which contains roasted and ground coffee and is provided with an elastic septum; by means of said cartridge it is possible to extract a beverage with improved physical and organoleptic characteristics with respect to espresso coffee obtained with traditional machines.
The beverage obtained with the cartridges described in the applications cited above can be obtained without having to reprogram particularly traditional espresso coffee machines but by using simply a particular extraction assembly which can be fixed at the hot water outlet.
For different reasons, a consumer is usually unable to drink an espresso coffee directly after its extraction by means of the traditional machine. This occurs often in restaurants, in which espresso coffee is brought to the table of the consumer a long time after its extraction, since typically many espressos are prepared at the same time and the waiter waits to be loaded with multiple cups before going to distribute them among the tables. Another reason why espresso coffee might not be drunk immediately after extraction is its high temperature.
Since the crema obtained in espresso coffee obtained with the traditional method has a relative short persistence, the time that separates the end of extraction from the moment when the espresso coffee is drunk can be so long that the espresso coffee loses part of the crema obtained with extraction, thus reducing the quality of the beverage at the time of consumption.
Moreover, again for different reasons, a consumer does not warm the cups before use, scarcely takes care to clean the machine, keeps the coffee exposed to the air for prolonged periods, uses the coffee assembly even when it is not properly heated, thus compromising the expected crema result.